More ingenuity harnessed in the name of commerce: the Shadow billboard is designed, quite literally, to only make sense when the sun comes out. The image, which advertises a brand of sunscreen, is composed of hundreds of small raised aluminium posts. When the sun is out and in the right place, the cast shadows form the image - a sunbathing woman. Interactive billboards aren't new - a while ago an environmental group put up a poster at, I think, Vauxhall Cross: it started out completely blank, and then as the days went by a message appeared as dark sooty particles accumulated on the surface, clinging to special glue.

Perhaps surprisingly, contemporary London isn't as festooned with billboards as it was in the Victorian era, when advertising pervaded every nook and cranny. This extract from Successful Advertising (1885) gives ten reasons when to stop advertising, one of which is: "When every man has become so thoroughly a creature of habit that he will certainly buy this year where he bought last year." As a result, public spaces were a riot of posters, all hawking this and that, in a totally unregulated, and unscrupulous market. Yet there has to be a happy medium between billboards so clever they detract totally from the experience of the sights, smells, people and activity of the city behind them (quite literally, as in the billboard photos of Stephen Gill) and the Delete! project, which stripped out all extraneous white noise from advertising in a single street in Vienna - creating a rather oppressive, dull space.

Simulated society may generate virtual culture, a New Scientist piece on the intention to simulate a community of 1,000 'intelligent' agents, observing how social groupings and structures emerge through the creation of simple tasks. The NEW-TIES project (wait for it, New and Emergent World models Through Individual, Evolutionary, and Social Learning. That's the kind of acronymn that was arrived at during an uninspired night at the pub) is a bit like The Sims but without humans to contaminate the gel in the petri dish. Other scientists scoff at the idea, which will include characters and environments modelled using Counter Strike to ensure it looks accessible and interesting for human observers. One Edward Castronava is quoted as saying, "The most sensible research project, it seems to me, would be to study [real human societies that grow up on their own within computer-generated fantasy worlds], rather than conjure artificial ones." Castranova has a proposal for a "university-based synthetic world", which he calls Arden. Smacks a bit of Live As a Tudor to me.